Scaling means in rock engineering clearing and loosening of loose rock after for example blasting in tunnelling, drifting etc. A known equipment for mechanized scaling includes a carrier vehicle, whereon is arranged a rotatable and pivotable scaling boom having an outer pivotal arm, at the free end of which is pivotally arranged a percussive hammer.
When performing the scaling operation with the known equipment, the operator is directing the hammer against the surfaces to be worked on by controlling the hydraulic cylinders of the boom arrangement. This means relatively complicated control work, since the operator has to control and compensate the different cylinders of the unit in dependent of the position of the boom with respect to the carrier vehicle. In practice, therefore, long term training is required for the operator to be able to handle the equipment at least somewhat efficiently with good precision.
One of the reasons for this is that the character of the scaling work is such that the equipment needs to be very robust and that different types of sensors are undesired. A solution with program control has therefore not been considered to be sufficiently reliable in the environment which prevails where the equipment is to be used. This is because the equipment constantly risks to be subjected to falling stones and even stone blocks.
Even if the above mentioned known scaling device is operated by an experienced and trained operator, its drawbacks lead to slow and thereby uneconomic procedure.
Aim and Most Important Features of the Invention
It is an aim of the present invention to provide a boom arrangement for a scaling device which allows better possibilities of control, and thereby provides provisions for more efficient and more economic scaling. This aim is achieved in a boom arrangement of the above mentioned kind through the features of the characterising portion of claim 1.
Hereby is achieved a boom geometry which allows an essentially more advantageous motion of the hammer essentially irrespective of which position the boom is standing in. In any case this concerns the positions that define the working area of the equipment. The greatest part of the scaling is typically performed in the roof of the space to be scaled, which means that a natural, horizontal movement of the hammer along the roof, which is achieved through the invention, is very suitable.
It is achieved through the invention with the pivoting of the boom column, an essentially horizontal movement of the hammer along a considerable length of the movement. According to the known art there is no corresponding horizontal movement achieved whatsoever. The small vertical movement which occurs because the upper end of the boom column, as well as the hammer itself, moves along a circular arch, can be essentially neglected in relation to the considerable horizontal movement which occurs in operation. The small vertical movement is very easily compensated for by the operator.
By it being so that the boom lift cylinder is positioned below the scaling boom, said cylinder is protected from falling stones.
Even if the invention is particularly advantageous for scaling work along horizontal surfaces such as tunnel roofs etc. it is also advantageously applicable for scaling on vertical surfaces such as tunnel walls etc. In this regard the invention is not inferior in comparison with the known art.
A scaling equipment as intended here works in a very unusual environment. It is common that very large pieces of rock falls down on the boom during operation. Through the invention, the boom lift cylinder will be protected against such pieces of rock to a high extent while maintaining the very advantageous working geometry which is provided by the further features of claim 1.
The central position of the cylinder which is made possible through the invention also brings along possibilities of enhanced view for the operator and enhanced rigidity for the boom.
The latter is of particular importance for scaling work sideways, when torsional stiffness is of great importance, which the forked embodiment allows.
It is preferred that the boom column and the column bar unit are essentially parallel and it is particularly preferred that the four-link mechanism forms a parallelogram. Hereby the lower pivot axes for the boom column and the column bar unit are preferably at the same horizontal level, whereby also the pivot axes of the column link formed with the boom column and the column bar unit are also positioned essentially on the same horizontal level for achieving said parallel displacement of the hammer.
When the support arm or the corresponding element is made in one piece with the column link, a stable and robust construction of these elements is achieved.
The boom column is preferably constructed with an enlarged lower portion having sideways considerably separated bearings for achieving the required sideways stability. In order to achieve the necessary stiffness of the boom column, that element has a section with at least partially U-shaped, or rectangular closed section.
Suitably the boom column is constructed such that with retracted boom column, the support arm or the corresponding element is retracted into a space formed in the upper portion of the column. This gives the possibility of a compact construction.
The corresponding advantages are obtained in connection with a scaling device according to claim 16.
Further features and advantages will be evident from the following detailed description of embodiments.